Method and apparatus for scheduling user equipment uplink transmissions on an unlicensed carrier

ABSTRACT

A method and apparatus schedule user equipment uplink transmissions on an unlicensed carrier. A configuration indicating a window length can be received from a higher layer, where the higher layer can be higher than a physical layer. A grant can be received in a subframe, where the grant can be for transmitting a physical uplink shared channel on a serving cell operating on an unlicensed carrier. A set of subframes for possible transmission of the physical uplink shared channel can be determined based on the window length and the subframe in which the grant is received. Listen before talk can be performed on the unlicensed carrier to determine an earliest unoccupied subframe in the set of subframes. The physical uplink shared channel can be transmitted in the earliest unoccupied subframe in response to receiving the grant.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to an application entitled “A Method andApparatus for Scheduling User Equipment Uplink Transmissions on anUnlicensed Carrier,” Motorola Mobility docket number MM01417 and anapplication entitled “A Method and Apparatus for Scheduling UserEquipment Uplink Transmissions on an Unlicensed Carrier,” MotorolaMobility docket number MM01418, both filed on even date herewith andcommonly assigned to the assignee of the present application, which arehereby incorporated by reference.

BACKGROUND

1. Field

The present disclosure is directed to a method and apparatus forscheduling user equipment uplink transmissions on an unlicensed carrier.

2. Introduction

Presently, users use portable devices, otherwise known as User Equipment(UE), such as smartphones, cell phones, tablet computers, selective callreceivers, and other wireless communication devices, on Long TermEvolution (LTE) networks. Users use the portable devices to downloadfiles, music, e-mail messages, and other data, as well as to watchstreaming video, play streaming music, play online games, surf the web,and engage in other data intensive activities. Because of large amountsof downloaded data as well as large amounts of users, LTE carriers cannow use unlicensed spectrum to complement the bandwidth of their LTEnetworks to provide faster data to users. This allows the users todownload data faster on their portable devices. The unlicensed spectrumcan include spectrum at 5 GHz, such as used by WiFi, and otherunlicensed spectrum. LTE technology can be deployed in unlicensedspectrum using a carrier aggregation framework where a primary cell useslicensed spectrum, and a secondary cell is deployed in the unlicensedspectrum. Transmissions on the unlicensed spectrum carrier typicallyhave to follow Discontinuous Transmission requirements (DCTrequirements) due to regulatory requirements and due the need toco-exist with other wireless systems, such as Wi-Fi systems, LTEdevices, such as UEs, and base stations, such as Enhanced Node-B's(eNBs), operating in the same spectrum. In some regulations, a LTEdevice may be required to perform Listen-Before-Talk (LBT) prior totransmitting on a carrier. If the device finds the channel is busy, thenit should defer its transmission until the carrier becomes clear.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which advantages and features of thedisclosure can be obtained, a description of the disclosure is renderedby reference to specific embodiments thereof which are illustrated inthe appended drawings. These drawings depict only example embodiments ofthe disclosure and are not therefore to be considered to be limiting ofits scope.

FIG. 1 is an example block diagram of a system according to a possibleembodiment;

FIG. 2 is an example flowchart illustrating a user equipment procedurefor a first option for transmitting a physical uplink shared channel onunlicensed carrier according to a possible embodiment;

FIGS. 3a and 3b are example flowcharts illustrating a user equipmentprocedure for transmitting a physical uplink shared channel onunlicensed carrier according to a possible embodiment;

FIGS. 4a and 4b are example flowcharts illustrating a user equipmentprocedure for transmitting a physical uplink shared channel onunlicensed carrier according to a possible embodiment;

FIG. 5 is an example illustration of uplink transmission with listenbefore talk according to a possible embodiment;

FIG. 6 is an example illustration of uplink transmission with listenbefore talk and sounding reference signal in first symbol of a subframeaccording to a possible embodiment;

FIG. 7 is an example flowchart illustrating a user equipment procedurefor transmitting a sounding reference signal according to a possibleembodiment;

FIG. 8 is an example block diagram of an apparatus according to apossible embodiment; and

FIG. 9 is an example block diagram of a base station according to apossible embodiment.

DETAILED DESCRIPTION

Embodiments can provide for a scheduling user equipment uplinktransmissions on an unlicensed carrier.

According to a possible embodiment, a configuration indicating a windowlength can be received from a higher layer, where the higher layer canbe higher than a physical layer. A grant can be received in a subframe,where the grant can be for transmitting a physical uplink shared channelon a serving cell operating on an unlicensed carrier. A set of subframesfor possible transmission of the physical uplink shared channel can bedetermined based on the window length and the subframe in which thegrant is received. Listen before talk can be performed on the unlicensedcarrier to determine an earliest unoccupied subframe in the set ofsubframes. The physical uplink shared channel can be transmitted in theearliest unoccupied subframe in response to receiving the grant.

According to another possible embodiment, a grant for transmittingphysical uplink shared channel on a serving cell operating on anunlicensed carrier can be received in a subframe. A set of subframes canbe determined for possible transmission of the physical uplink sharedchannel. Listen before talk can be performed on the unlicensed carrierto determine an earliest unoccupied subframe in the set of subframes. Aphysical uplink shared channel can be transmitted in multiple subframeswithin the set of subframes on the unlicensed carrier, starting with theearliest unoccupied subframe, in response to receiving the grant.

According to another possible embodiment, listen before talk can beperformed to determine when a subframe is available for uplinktransmission. A sounding reference signal can be transmitted in a firstdiscrete Fourier transform spread orthogonal frequency divisionmultiplexing symbol of the subframe when listen before talk indicatesthat the subframe is available. A physical uplink shared channel can betransmitted in at least a portion of a remaining part of the subframe.

FIG. 1 is an example block diagram of a system 100 according to apossible embodiment. The system 100 can include a first User Equipment(UE) 110 and a base station 120. The base station 120 can be an EnhancedNode-B (eNB), such as a cellular base station, a Long Term Evolution(LTE) base station, or any other base station. The first UE 110 and thebase station 120 can communicate on different cells 130 and 140. Thecell 130 can be a first cell, such as a primary cell and the UE 110 canbe connected to the primary cell. The cell 140 can be a second cell,such as a secondary cell. Furthermore, the second cell 140 can be a cellthat operates on unlicensed spectrum. The cells 130 and 140 can also becells associated with other base stations, can be a macro cells, can bemicro cells, can be femto cells, and/or can be any other cells usefulfor operation with a LTE network. The system 100 can also include asecond UE 112 that can communicate with the base station 120 on cells132 and 142 in a similar manner to the first UE 110, where the cell 132can be a primary cell and the cell 142 can be a secondary cell. The UEs110 and 112 can be any devices that can access a wireless wide areanetwork. For example, the UEs 110 and 112 can be wireless terminals,portable wireless communication devices, smartphones, cellulartelephones, flip phones, personal digital assistants, personal computershaving cellular network access cards, selective call receivers, tabletcomputers, or any other device that is capable of operating on awireless wide area network.

In operation, UE uplink Physical Uplink Shared Channel (PUSCH)transmissions can be supported using different approaches. For FrequencyDivision Duplex (FDD) with Transmission Time Interval (TTI) bundlingdisabled, if a UE receives an uplink grant in subframe n from an eNB, itcan transmit PUSCH in subframe n+4 in response to that grant. For LTE, asubframe typically can have a 1 ms duration. For example, the 4 subframeduration between grant reception and UE transmission can be the maximumduration allowed for UE hardware processing, such as the time needed bythe UE hardware to decode the grant and prepare the PUSCH transmission.The value “4” is an example value used throughout this disclosure, butin principle, it is possible to have a different value. For example,‘n+4’ can effectively mean ‘n+dmax’ where dmax can be a maximum durationallowed for UE hardware processing after receiving a grant in subframen. For FDD with TTI bundling enabled, if a UE receives an uplink grantin subframe n, it can transmit PUSCH in a predefined set of subframes{n+4, n+5, . . . n+4+L−1} in response to that grant, where L can beconfigured by higher layers that are higher than the physical layer. ForTime Division Duplex (TDD), if a UE receives an uplink grant in subframen, it can transmit PUSCH in a predefined subframe n+k in response tothat grant, where k can be determined from predefined table(s) in an LTEspecification. For TDD with TTI bundling enabled, if a UE receives agrant in subframe n, the UE can transmit PUSCH in a predefined set ofsubframes {n+k1, n+k2, . . . n+kL} in response to that grant, where L,k1, and k2 . . . kL can be determined from predefined table(s) in thespecification. For TDD, if an ‘ul index’ field, such as TDDUplink/Downlink (UL/DL) configuration 0, is transmitted in the uplinkgrant and if a UE receives the uplink grant in subframe n, the UE cantransmit PUSCH in a predefined subframe n+k, n+7, or both subframes, inresponse to that grant, depending on the ‘ul index’ field setting in thegrant, where k can be determined from predefined table(s) in thespecification. In all the above approaches, the UE can transmit PUSCH inone or multiple predefined subframes in response to receiving a grant.

For operation in unlicensed spectrum due to regulatory requirements, anddue the need to co-exist with other wireless systems, such as Wi-Fi, andLTE devices, such as UEs and eNBs, before transmitting on an unlicensedcarrier, the LTE devices, such as UEs typically have to check whetherthe carrier is busy using some form of ‘Listen Before Talk’ (LBT)mechanism, and can begin transmissions only if the carrier is free. LBTtypically can include measuring energy on the carrier, sometimesreferred to as sensing, for a short duration, such as 9 us or 20 us, anddetermining whether the measured energy is less than a threshold, suchas −82 dBm or −62 dBm. If the energy is less than the threshold, thecarrier is determined to be free. Some examples of LBT can include theClear Channel Assessment-Energy Detect (CCA-ED) and Clear ChannelAssessment-Carrier Sense (CCA-CS) mechanisms defined in IEEE 802.11specifications, CCA mechanisms specified in the ETSI EN 301 893specification, and other forms of LBT. Transmissions on the carriertypically also have to follow Discontinuous Transmission (DCT)requirements. For example, an LTE device, such as a UE, can continuouslytransmit for Xms, such as where X can be 4 ms as per some regulationsand up to 13 ms for some other regulations, after which it may have tocease transmission for some duration, sometimes referred as an idleperiod, perform LBT again, and reinitiate transmission only if LBT issuccessful. The LTE device may perform LBT towards the end of the idleperiod.

Therefore, for operation in unlicensed spectrum, after a UE receives agrant from an eNB indicating the UE to perform transmission inunlicensed spectrum, the UE often may have to perform LBT, and transmitonly if LBT is successful, such as when the carrier is determined to befree. The terms LBT and CCA are used interchangeably in the disclosedembodiments. Both terms refer to the aspect of the device having tocheck whether the carrier is free before transmission. If the carrier isbusy, the UE may not transmit, such as when it has to skip a PUSCHtransmission, and may have to wait for another scheduling grant from theeNB. For example, if a UE receives a grant in subframe n fortransmission in subframe n+4, the UE may have to perform LBT thatenables UE transmission in subframe n+4. If the carrier is free, the UEcan transmit PUSCH in subframe n+4. If the carrier is busy, the UE mayhave to skip the transmission in subframe n+4 and wait for anothergrant. Since the eNB may not accurately predict in advance, such as insubframe n, when the carrier will be free near the UE, this approach maybe inefficient, as it can lead to a number of skipped UE transmissionswith each skipped UE transmission leading to an extra grant. Thus,embodiments can provide signaling enhancements that can address theseand other issues.

Some embodiments can provide signaling enhancements that give a UEmultiple transmission opportunities for each received grant, and let theUE determine the subframe where the PUSCH is transmitted based oncarrier availability, such as based on the result of LBT. An eNB candetect which transmission opportunities a UE has utilized based on, forexample, blind detection. Allowing too much flexibility to the UE mayincrease eNB complexity, where the eNB receiver may have to blindlydetermine the subframe in which the PUSCH is transmitted by the UE.Given this, some embodiments provide signaling approaches that providegood trade-offs between UE transmission flexibility and eNB complexity.For some embodiments, the UE can be configured with a Primary cell(Pcell) that can operate on a licensed carrier and a Secondary cell(Scell) that can operate on an unlicensed carrier. The grant in responseto which the UE transmits PUSCH on the unlicensed carrier can bereceived by the UE on either the Pcell, such as on a licensed carrier,or the Scell, such as on an unlicensed carrier. The UE can perform LBTusing the mechanisms described below. For some embodiments, the UE cansend a Hybrid Automatic Repeat Request Identifier (HARQ ID) and HARQ subidentifier (HARQ subID) along with its PUSCH transmission orretransmission using the mechanisms described below.

FIG. 2 is an example flowchart 200 illustrating a UE procedure for afirst option for transmitting PUSCH on unlicensed carrier according to apossible embodiment. At 205, the flowchart 200 can begin. At 210, a UEcan be configured via higher layers with a transmission opportunitywindow length (W), where W can be 1, 2, 3, or 4 subframes, and where W=1can correspond to current LTE operation, such as a default value. Thewindow length (W) may also be set to any other useful value.

At 220, the UE can receive an uplink grant in subframe n. The grant cancontain bits indicating a HARQ ID, such as a 3 bit HARQ-ID. The numberof bits used for indicating the HARQ ID may depend on a maximum numberof HARQ processes (M_UL_HARQ). For example, for LTE uplink, the maximumnumber of HARQ processes can be either 8 for non-Multiple Input MultipleOutput (MIMO) uplink or 16 for MIMO uplink (UL-MIMO) per componentcarrier. For UL-MIMO, two HARQ processes associated with the subframe nmay be HARQ ID and HARQ ID+8 for transport block 1 and transport block 2respectively, that may require indication of only HARQ ID for the lowestindex, such as the enabled, transport block in the uplink grant. In thiscase, M_UL_HARQ can be set to 8. A transport block can be the data fromthe upper layer, such as a Medium Access Control (MAC) layer, given tothe physical layer in a LTE system. Signaling of the HARQ ID canexplicitly enable an eNB to schedule an uplink transmissionasynchronously. For example, the retransmissions for a given uplink HARQprocesses may be adaptable in time and need not occur with a fixed RoundTrip Time (RTT). The uplink grant received by the UE can also containbits indicating modulation and coding scheme (MCS) to be used for PUSCHtransmission, bits indicating a resource allocation (RA) within asubframe, such as the Resource Blocks (RBs) within a subframe to use forPUSCH transmission, bit(s) indicating whether the grant is for new data,such as a grant for an initial or new transmission, or indicating thegrant is retransmission (for example, by using a 1 bit New DataIndicator (NDI)), and other bits indicating additional controlinformation.

If the UE receives an uplink grant with HARQ ID x in subframe n, inresponse to the grant, the UE can attempt to transmit PUSCH in subframen+4. If the carrier is not free for transmission in subframe n+4, suchas when LBT is not successful, the UE can attempt PUSCH transmissions insubsequent subframes until a subframe is free or until the window length(W) is reached. For example, at 230, a counter j can be set to zero. At240, the UE can perform LBT for transmitting PUSCH in subframe n+4+j. At250, the UE can determine whether the carrier is free based on theresults of LBT.

If the carrier is free, at 260, with each PUSCH transmission, the UE caninclude the associated HARQ ID, such as the HARQ ID provided by thegrant in response to which the PUSCH transmission is being made and theflowchart can end at 295. The HARQ ID can be implicitly communicated bya Demodulation Reference Signal (DMRS), such as a cyclic shift for theDMRS and Orthogonal Cover Code (OCC) index, associated with the PUSCHtransmission. Alternately, the HARQ ID can be explicitly sent as part ofthe PUSCH transmission.

If the carrier is not free, at 270, the UE can increment the counter j.At 280, the UE can determine if the counter is still below the windowvalue (W). If it is, the flowchart 200 can return to 240 and continueaccordingly. If the counter has reached the window length value (W), at290, the UE can skip the PUSCH transmission for the HARQ ID (x) inresponse to the grant received in subframe n. At 295, the flowchart 200can end.

If the UE has PUSCH transmissions for multiple grants queued up due tolack of carrier availability in previous transmissions, the UE canprioritize the PUSCH transmission corresponding to the earliest grant.For example, if the UE receives a grant in subframe n, such as for HARQID (x₁), and another grant in subframe n+1, such as for HARQ ID (x₂),and if LBT fails for subframe n+4 but is successful for subframe n+5,the UE can transmit the PUSCH corresponding to grant received insubframe n, such as the PUSCH corresponding to HARQ ID (x₁), and canattempt to transmit the PUSCH corresponding to HARQ ID (x₂) insubsequent subframes until the window length (W) is reached.Alternatively, higher layers may indicate the priority for HARQ ID's,and the UE can follow the priority order in determining which HARQ ID isprioritized for transmission, when multiple HARQ ID's have pendingtransmission. Alternatively, the UE can prioritize PUSCH transmissionsbased on its own prioritization rules, for example, based on the type oftraffic associated with the PUSCH transmission. In another example, ifLBT fails in subframe n+4 and succeeds in subframe n+5, if a power headroom report becomes available in subframe n+4 or subframe n+5, the UEcan transmit a PUSCH containing the power head room report in subframen+5.

The window length (W) can be an eNB implementation choice. For example,if an eNB picks W=4, the UE can get 4 attempts to transmit PUSCH for agiven uplink grant, but the eNB may have to blindly attempt to decodePUSCH corresponding to a maximum of 4 separate grants for each scheduledUE in each subframe. If the eNB picks W=1, blind detection of PUSCH isnot necessary, but the UE has only one attempt/transmission opportunityto send PUSCH and the UE can be more likely to skip the PUSCHtransmission if LBT is not successful, such as when the channel is busy.Given the trade-offs involved, the eNB can pick a value for W dependingon factors such as loading of the operating carrier and/or Quality ofService (QoS) requirements for the UE's UL traffic. In a first example,the eNB can pick a smaller value for W, such as W=1, when it determinesthat the carrier is mostly free, such as when LBT at the UE is more liketo succeed, and can pick a larger value of W, such as W=4, when thecarrier is busy, such as when LBT at the UE is less likely to succeed.In a second example, the eNB can pick a larger value of W whilescheduling delay sensitive traffic and a smaller value of W for besteffort traffic. In a third example, the eNB can pick a larger value of Wfor UEs whose PUSCH transmission subframes can be blindly detected withmore confidence, such as for UEs that are closer to the eNB whosesignals will be received by the eNB with higher SNR and hence thepresence/absence of PUSCH from those UEs can be determined with moreconfidence than UEs with low receive SNR.

FIGS. 3a and 3b are example flowcharts 301 and 302 illustrating a UEprocedure for a second option for transmitting PUSCH on unlicensedcarrier for initial transmission and retransmission according to apossible embodiment.

In the first option, when the eNB configures W>1 and sends a grant to aUE indicating PUSCH transmission in a certain set of RBs, the RBs may beblocked for all subframes falling within the transmission window W. Forexample, if W=4 and a grant is sent in subframe n, indicating PUSCHtransmission in RBs 1-10, the UE can be allowed to transmit PUSCH in RBs1-10 in subframes n+4, n+5, n+6, n+7. Since, the eNB does not know whichsubframe the UE may transmit; it cannot schedule those RBs for otherUEs. Multiple User Multiple Input Multiple Output (MU MIMO) can bepossible, albeit with possible restrictions, such as based on availableDMRS cyclic shifts, same RB allocations for all the MU co-scheduled UEs.Also, since the UE transmits PUSCH in only one subframe of the window,the RB allocation for other subframes may be wasted even if the carrieris free. For example, for a grant sent in subframe n, if LBT at the UEsucceeds for subframe n+4, the RBs 1-10 for subframes n+5, n+6 and n+7are left unused. The eNB can send grants to the UE in subframes n+1,n+2, n+3 . . . assuming that the carrier is free in subframes n+5, n+6,n+7 respectively, but if the carrier is busy, the grants can be wasted,which may lead to unnecessary DL control overhead. The second option canattempt to address this issue by enabling the UE to make multiple PUSCHtransmissions in response to a single grant. Compared to the firstoption, the second option may require additional bits in DownlinkControl Information (DCI), such as 2 extra bits if W=4, 3 extra bits ifW=8, etc.

At 305, the flowchart 301 can begin. At 310 a UE can receive an uplinkgrant in subframe n. The grant can contain bits indicating the HARQ ID(x), such as a 3 bit HARQ-ID. The grant can also contain bit(s)indicating whether the grant is for new data, such as an initialtransmission or a new transmission, or the grant is not for new data,such as by using 1 a bit New Data Indicator (NDI). The grant canadditionally contain additional bits, such as 2 bits. For the additionalbits, if the grant is for new data, such as an initial transmission,based on a NDI toggle, the additional bits can indicate a window length(W). For example, 00 can indicate W=1 subframe, 01 can indicate W=2subframes, 10 can indicate W=3 subframes, and 11 can indicate W=4subframes. If the grant is for retransmissions, such as when NDI is nottoggled, the additional bits can indicate a HARQ subID of the packet forwhich the retransmission is requested. The number of additional bitsused can depend on the maximum allowed window length (Wmax). This can befixed in the specification. Alternately, this can be a configurablevalue, indicated to the UE via higher layers. For example, if a RadioResource Control (RRC) indicates Wmax=8, the UE can expect the UL grantsto have 3 additional bits to indicate the ‘window length (W) or the HARQsubID’. The uplink grant received by the UE can also contain bitsindicating a modulation and coding scheme (MCS) to be used for PUSCHtransmission(s), bits indicating a resource allocation (RA) within asubframe, such as the RBs to use for PUSCH transmission(s), and otherbits indicating additional control information.

If at 312, the NDI bit(s) indicate that the grant is for an initialtransmission, the rest of flowchart 301 can be utilized. In particular,in response to the grant received in subframe n, the UE can transmitPUSCH in subframe n+4 if the LBT for subframe n+4 is successful. If theUE still has data in its UL buffer, the UE can transmit PUSCH insubframe n+5 in response to the same grant received in subframe n, ifthe LBT for subframe n+5 is also successful. The UE can continuetransmitting PUSCH in subsequent subframes if LBT is successful forthose subframes and the UE has data in its UL buffer until the windowlength (W) signaled in the grant is reached. With each PUSCHtransmission, the UE can include the associated HARQ ID that wasprovided by the grant in response to which the PUSCH transmission(s) arebeing made.

Since multiple PUSCH transmissions can be made in response to one grantand one HARQ ID, with each PUSCH transmission, the UE can also include aHARQ subID to enable the eNB to individually identify each PUSCHtransmission. For an example when the grant received in subframe n has aHARQ ID of zero (x=0) and window length W=4, and assuming LBT issuccessful for all subframes for the window, the HARQ subID (y) can beset where the UE can send x=0 and y=0 for the first PUSCH transmissionmade in response to the grant in subframe n+4, where x is the HARQ IDand y is the HARQ subID. Then, if the UE UL buffer is not empty, the UEcan send x=0 and y=1 for the second PUSCH transmission made in responseto the grant in subframe n+5. If the UE UL buffer is still not empty,the UE can send x=0 and y=2 for the third PUSCH transmission made inresponse to the grant in subframe n+6. If the UE UL buffer is still notempty, the UE can send x=0 and y=3 for the fourth PUSCH transmissionmade in response to the grant in subframe n+7.

For an example where the grant received in subframe n has a HARQ ID ofzero (x=0), and a window length W=4 and assuming LBT is unsuccessful forsubframe n+4 and n+6, but successful for subframes n+5 and n+7, the HARQsubID (y) can be set where the UE can send x=0 and y=0 for the firstPUSCH transmission made in response to the grant in subframe n+5. If theUE UL buffer is not empty, the UE can send x=0 and y=1 for the secondPUSCH transmission made in response to the grant in subframe n+7. Whenthe eNB has to request a retransmission of a PUSCH that was transmittedby the UE along with HARQ ID (x) and HARQ subID (y), the eNB can includethe same HARQ ID (x) and HARQ subID (y) in the re-transmission grantsent to the UE and can set the NDI bit(s) to indicate a retransmissionrequest.

For example, if at 312, the NDI bit(s) indicate that the grant is for aninitial transmission, at 314, the HARQ subID can be set to 0 (y=0). Thewindow length (W) can be determined using bit(s) indicating the ‘windowlength (W) or HARQ subID (y)’ (for example, if the grant is for aninitial transmission, the UE can use those bits for determining windowlength (W); if the grant is for a re-transmission the UE can use thosebits for determining HARQ subID). At 316, a counter j can be set tozero. At 318, LBT can be performed for transmitting in subframe n+4+j.If at 320, LBT indicates the carrier is not free, at 322, the counter jcan be incremented. If at 324 the counter j has not reached the windowlength (W), LBT can be performed in a next subframe at 318.

If the carrier is free at 320, then at 326, PUSCH transmissions can beperformed in subframe n+4+j and the PUSCH/DMRS can include the HARQ IDand the HARQ subID. If the UE uplink buffer is not empty at 328, at 330the HARQ subID can be incremented, i.e., y=y+1. If the UE uplink bufferis empty at 328 or if the counter j has reached the window length (W) at324, at 332 PUSCH transmissions can cease for the grant received insubframe n for that particular HARQ ID and at 334, the flowchart 301 canend.

If at 312, the NDI bit(s) indicate that the grant is for aretransmission, the flowchart 301 can advance to 336 to branch to step350 of flowchart 302. In particular, in the flowchart 302 the additionalbits in the grant can indicate the HARQ subID of the correspondinginitial transmission for which PUSCH retransmission is requested asdescribed earlier. The window length (W) can be the window lengthdetermined by the UE for the corresponding initial transmission forwhich the PUSCH retransmission is requested. The UE can attempt to makethe PUSCH retransmission in subframe n+4, and, if the carrier is notfree for transmission in subframe n+4, such as when LBT is notsuccessful for that subframe, the UE can attempt PUSCH retransmission insubsequent subframes until a subframe is available or until the windowlength is reached. The UE can include the HARQ ID and HARQ subIDindicated by the retransmission grant along with its PUSCHretransmission. Note that unlike the initial/new transmission case, theUE may only send one PUSCH retransmission in response to a grant thatindicates a retransmission.

For example, at 350 the flowchart 302 can begin. At 352, the windowlength (W) can be set based on the initial transmission. The HARQ subIDcan be determined using bits indicating the ‘window length (W) or theHARQ subID transmitted’ in the grant (for example, if the grant is foran initial transmission, the UE can use those bits for determiningwindow length (W); if the grant is for a re-transmission, the UE can usethose bits for determining HARQ subID). At 354, a counter j can be setto zero. At 356, LBT can be performed for transmitting PUSCH in subframen+4+j on a carrier. If at 358 LBT indicates the carrier is free, at 360PUSCH transmission can be performed in subframe n+4+j. The PUSCH/DMRScan include the HARQ ID, such as x, and the HARQ subID, such as y. If at358 LBT indicates the carrier is busy, at 362 the counter j can beincremented. If at 364 the counter j is less than the window length (W),at 356 LBT can be performed for the next subframe. If the counter j hasreached the window length (W), at 366, the PUSCH retransmission can beskipped for the HARQ ID and the HARQ subID indicated in the grantreceived in subframe n. At 368, the flowchart 302 can end.

FIGS. 4a and 4b are example flowcharts 401 and 402 illustrating a UEprocedure for a third option for transmitting PUSCH on unlicensedcarrier for initial transmission and retransmission according to apossible embodiment. In the second option above, the UE may need tosignal additional HARQ subID bits in addition to the HARQ ID bits alongwith its PUSCH transmissions to identify the individual PUSCHtransmission(s) that are made in response to a single grant. Forexample, assuming 3 bits for HARQ ID and 2 bits for HARQ subID, the UEmay have to send a total of 5 bits along with each of its PUSCHtransmission. A third option can attempt to address this issue byavoiding the need to transmit a HARQ subID.

For the third option, at 405, the flowchart 401 can begin. At 410, a UEcan receive a window length (W). The window length (W) can be configuredby higher layers or the window length (W) can be signaled using bits ina uplink grant. At 412, the UE can receive an uplink grant in subframen. The grant can contain bits indicating HARQ ID. For example, 3 bitscan be used to indicate HARQ ID. The grant can also contain bit(s)indicating whether the grant is for new data, such as an initialtransmission or new transmission, or not. For example this can be done,such as by using a 1 bit NDI. The uplink grant received by the UE canfurther contain bits indicating a Modulation and Coding Scheme (MCS) tobe used for PUSCH transmission(s), bits indicating Resource Allocation(RA) within a subframe, such as RBs to use for PUSCH transmission(s),and other bits indicating additional control information.

If at 414 the NDI bit(s) indicate that the grant is for an initialtransmission, in response to the grant received in subframe n, the UEcan transmit PUSCH in subframe n+4 if the LBT for subframe n+4 issuccessful. If the UE still has data in its UL buffer and if the LBT forsubframe n+5 is also successful, the UE can transmit PUSCH in subframen+5 in response to the same grant received in subframe n. The UE cancontinue transmitting PUSCH in subsequent subframes if LBT for thosesubframes is successful and the UE still has data in its UL buffer untila window length (W) is reached.

With each PUSCH transmission, the UE can include an associated HARQ ID(x′), where x′ is the value of the associated HARQ ID. The associatedHARQ ID (x′) transmitted by the UE can be determined from the HARQ ID(x) provided by the grant, such as the grant in response to which thePUSCH transmission(s) are being made. According to a possibleimplementation, the value of the associated HARQ ID (x′) can bedetermined using a formula x′=MOD(x+offset_value, M_UL_HARQ), where‘offset_value’ is set to 0 for the first PUSCH transmission, and isincremented by one for each additional PUSCH transmission made inresponse to the same grant, M_UL_HARQ is the Maximum number of UL HARQprocesses, and x is the HARQ ID sent with the uplink grant. TheM_UL_HARQ value can be defined in the specification or set by higherlayers. The formula can limit x′ to the M_UL_HARQ and other equations orprocesses can be used for the same effect. For an example where thegrant received in subframe n has HARQ ID x=0 and window length W=4,assuming LBT is successful for all subframes for the window, andassuming M_UL_HARQ=8, the UE can send associated HARQ ID x′=0 for thefirst PUSCH transmission made in response to the grant in subframe n+4.If the UE UL buffer is not empty, the UE can send associated HARQ IDx′=1 for the second PUSCH transmission made in response to the grant insubframe n+5. If the UE UL buffer is still not empty, the UE can sendassociated HARQ ID x′=2 for the third PUSCH transmission made inresponse to the grant in subframe n+6. If the UE UL buffer is still notempty, UE can send associated HARQ ID x′=3 for the fourth PUSCHtransmission made in response to the grant in subframe n+7.

For an example where the grant received in subframe n has HARQ ID x=0and window length W=4, assuming LBT is unsuccessful for subframe n+4 andn+6 but successful for subframes n+5 and n+7, and assuming Maximumnumber of UL HARQ processes=8, the UE can send associated HARQ ID x′=0for the first PUSCH transmission made in response to the grant insubframe n+5. If the UE UL buffer is not empty, the UE can sendassociated HARQ ID x′=1 for the second PUSCH transmission made inresponse to the grant in subframe n+7.

For example, at 416, a counter j can be set to 0 and the offset_valuecan be set to 0. At 418, LBT can be performed for transmitting PUSCH insubframe n+4+j. If at 420, the carrier is not free, at 422, the counterj can be incremented by 1. If j is less than the window length (W) at424, then LBT can be performed for a next subframe at 418. If at 420,the carrier is free, at 426, x′ can be set to MOD(x+offset_value,M_UL_HARQ). At 428, the PUSCH transmission can be performed in subframen+4+j and PUSCH/DMRS can include the associated HARQ ID indication x′.If at 430 the UE uplink buffer is not empty, at 432 the offset_value canbe incremented and the process can continue at 422. If the uplink bufferis empty at 430 or the counter j has reached the window length (W) at434, the PUSCH transmissions can stop for HARQ ID x for the grantreceived in subframe n. At 438, the flowchart 401 can end.

If at 414, the NDI indicates a retransmission, then the UE can determinethat the eNB has requested a retransmission of a PUSCH that wastransmitted by the UE with associated HARQ ID (x′). In theretransmission grant, the eNB can include the same HARQ ID (x′) as theassociated HARQ ID (x′) that was previously sent by the UE, and sets theNDI bit(s) to indicate a retransmission request. The flowchart 401 canthen advance to step 450 of flowchart 402 via step 436. The UE can thenattempt to make the PUSCH retransmission in subframe n+4, and if thecarrier is not free for transmission in subframe n+4, such as when LBTfor subframe n+4 is not successful, the UE can attempt PUSCHretransmission in subsequent subframes until a subframe is available oruntil the window length (W) is reached. If a subframe counter j getsincremented for multiple subframes and does not remain smaller thanwindow length (W), the UE can skip the PUSCH retransmission for HARQ IDx′ in response to the grant received in subframe n. When LBT determinesthe carrier is free, the UE can include the same associated HARQ ID (x′)indicated by the retransmission grant along with its PUSCHretransmission. Unlike the initial transmission case, the UE may onlysend one PUSCH retransmission in response to a grant that indicates aretransmission.

For example, at 452, a counter j can be set to 0. At 454, LBT can beperformed for transmitting PUSCH in subframe n+4+j. If the carrier isfree at 456, at 458 a PUSCH transmission can be performed in subframen+4+j and PUSCH/DMRS can include the HARQ ID indication (x′) and theflowchart can end at 466. If the carrier is not free at 456, at 460 thecounter j can be incremented. If at 462 the counter j is less than thewindow length W, at 454 LBT can be performed for transmitting PUSCH in anext subframe. If at 462 the counter j has reached the window length, at464 the PUSCH transmission can be skipped for HARQ ID x′ from the grantreceived in subframe n. At 466, the flowchart 402 can end.

A UE procedure for a fourth option for transmitting PUSCH on unlicensedcarrier for initial transmission and retransmission according to apossible embodiment can attempt to avoid a requirement for the UE totransmit HARQ ID along with its PUSCH transmissions. For example, thesecond option discussed above may require the UE to send the HARQ ID andalso a HARQ sub ID, along with each PUSCH transmission to enable the eNBto uniquely identify the Transport Block(s) (TB(s)) associated with thatPUSCH transmission. The third option discussed above may require the UEto send an associated HARQ ID, along with each PUSCH transmission toenable the eNB to uniquely identify the Transport Block(s) (TB(s))associated with that PUSCH transmission. The fourth option can avoid theneed for the UE to transmit HARQ ID along with its PUSCH transmissions.Compared to the second and third options, the fourth option can reducescheduler flexibility for the eNB, but can also result in smaller uplinktransmission overhead.

In the fourth option, the UE can receive a grant in subframe n. Thegrant can contain bits indicating a HARQ ID (x) and the grant can alsocontain bits indicating a window of subframes with window length (W) inwhich the UE can transmit PUSCH in response to the grant. Alternatively,window length information can be sent to the UE via higher layersinstead of including bits in the grant, which can reduce grant payloadoverhead. The grant can also include bit(s) indicating whether the grantis for a new transmission or a retransmission, such as by using NDIbits. The grant can contain multiple NDI bits, where each NDI bit (p)can correspond to one subframe (subframe n+4+m) in the window ofsubframes. For example, if the window length W=4, the grant can contain4 NDI bits with the first bit corresponding to PUSCH transmission insubframe n+4, the second bit corresponding to PUSCH transmission insubframe n+5, and so on. The uplink grant received by the UE can alsocontain bits indicating a MCS to be used for PUSCH transmission(s), bitsindicating Resource Allocation (RA) within a subframe, such as the RBsto use for PUSCH transmission(s), and other bits indicating additionalcontrol information.

In response to the grant received in subframe n, the UE can make PUSCHtransmissions in each subframe (subframe n+4+m) of the window ofsubframes for which LBT is successful. For subframes where the LBT isnot successful, the UE can skip the PUSCH transmission and can wait forthe eNB to send another grant requesting retransmission. The HARQ ID foreach PUSCH transmission can be determined implicitly based on thesubframe index of the subframe used for PUSCH transmission and the HARQID signaled in the grant. For example, if the grant in subframe ncontains HARQ ID x, the UE's PUSCH transmission in subframe n+4+m cancorrespond to HARQ ID x″ where x″=MOD (x+m, M_UL_HARQ), and where 0<m<Wis the position of the subframe within the window of subframes. Sincethe HARQ ID can be implicitly linked to subframe index (e.g. n+4+m),there may be no need for the UE to transmit the HARQ ID along with itsPUSCH transmission. That is, the eNB can implicitly determine the HARQID x″ using the subframe index of the subframe in which PUSCHtransmission is received from the UE (e.g. n+4+m), and the HARQ ID sentby the eNB in the grant (e.g., x) and the maximum number of uplink HARQprocesses (M_UL_HARQ).

Additional embodiments can provide options for performing LBT for uplinktransmissions by the UE. For a PUSCH transmission in a subframe, such assubframes n+4 or n+5, according to a first possible implementation, theUE can start performing LBT in the time duration corresponding to thelast Orthogonal Frequency multiplexing/Discrete Fourier Transform(OFDM/DFT)-Spread OFDM(A) (DFT-SOFDM(A)) symbol in a previous subframe,such as in subframe n+3 or n+4 respectively. DFT-SOFDM(A) can also bereferred to as Single Carrier FDM(A) (SC-FDM(A)). According to secondpossible implementation, the UE can start performing LBT in the timeduration corresponding to the first DFT-SOFDM symbol in the samesubframe, such as subframes n+4, n+5 respectively. According to a thirdpossible implementation, for each burst of contiguous PUSCHtransmissions in multiple subframes, such as subframes {n+4, n+5, . . .}, the UE can start performing LBT in the time duration corresponding tomultiple ending OFDM/DFT-SOFDM symbols of a subframe immediatelypreceding the burst, such as in subframe n+3.

The eNB can send higher layer signaling to the UE based on which the UEcan determine the minimum time duration for which it has to perform LBTbefore initiating a PUSCH transmission. The UE may also determine themaximum number of contiguous subframes in which it can transmit usinghigher layer signaling from the eNB. For example, the eNB can signal a‘q’ value as specified in ETSI EN 301 893 specifications, such as in aclause describing channel access mechanism for load based equipment viahigher layers. The UE can use the ‘q’ value to determine the minimumtime duration for which it has to do LBT, such as using CCA and extendedCCA mechanisms, before initiating the PUSCH transmission. The UE canalso determine the maximum of contiguous subframes in which it cantransmit PUSCH by deriving the maximum channel occupancy time using the‘q’ value.

To support scheduling of multiple UEs transmissions in the samesubframe, UEs may need to perform LBT operations in the same timewindow. The transmission in the previous subframe may originate from theeNB (downlink) or another UE(s) (uplink). The eNB may configure the UEsto start performing LBT assessments no earlier than T1 sec from thestart of the guard period, such as a last OFDM/DFT-SOFDM symbol durationin the first implementation, and end LBT no later than T2 sec from thestart of the PUSCH transmission if CCA is successful. T1 and T2 mayinclude Tx/Rx switching time and expected worst case propagation delay.The eNB may also configure the same or substantially similar, such aswithin a few us, Timing Advance (TA) value for the UEs. The TA value maybe a fixed value TA1, such as 624 Ts, in the specification.

If a UE using the second option above performs LBT using the secondimplementation, then the UE may need to perform LBT only once for eachburst of contiguous PUSCH transmission subframes, instead of once foreach PUSCH transmission subframe. For example, for the processillustrated in flowchart 401, while the UE may have to perform LBT andcheck if the carrier is free for PUSCH transmission corresponding tosubframe where j=0, it can also skip the step of performing LBT andchecking if carrier is free for other values of j. If devices operatingon the unlicensed carrier have to follow a maximum occupancy timerequirement, the eNB can be expected to signal a W value that is roughlyequal to the maximum channel occupancy time requirement.

FIG. 5 is an example illustration of an uplink transmission 500 with LBTaccording to a possible embodiment.

Typically for normal Cyclic Prefix (CP) there are 14 symbols in an LTEsubframe (uplink or downlink), where each symbol can correspond toroughly 70 us duration. For a UE to perform uplink transmission insubframe n+4, the UE may have to perform LBT in the last DFT-SOFDMsymbol of the previous subframe. If the previous subframe (n+3) was anuplink subframe, the UE would have to shorten its PUSCH transmissions insubframe n+3. The last symbol of an uplink subframe is typicallyreserved for PUSCH or SRS (Sounding Reference Signal) transmission fromthe UE to help eNB scheduling. Since LBT can disallow SRS transmissionsin the last symbol, an alternate method can be useful to allowtransmission of SRS from the UE to the eNB.

FIG. 6 is an example illustration of uplink transmission 600 with LBTand SRS in a first DFT-SOFDM symbol of a subframe according to apossible embodiment. There may be three types of UE transmission on theuplink in unlicensed spectrum. For SRS transmission only, since a UEsLBT can disallow SRS transmissions in the last symbol of an uplinksubframe, an alternate location for SRS transmission can be used. The UEcan transmit SRS as soon as it senses a channel is free. Otherwise, theUE may have to transmit a reservation signal to keep the channeloccupied until the time it is allowed to transmit the SRS. The UE cantransmit the SRS in the first DFT-SOFDM symbol of an uplink subframe.This can allow a UE to do LBT immediately prior to the DFT-SOFDM symboland transmit whenever the channel is free. To ensure that other UEs thatare only performing PUSCH transmissions in that subframe are notaffected, the eNB can signal to the other UEs to avoid PUSCH mapping tothe first DFT-SOFDM symbol of the subframe.

For PUSCH transmission only, a shortened PUSCH can be used, where noPUSCH is transmitted in the symbol reserved for LBT. PUSCH may not betransmitted in the first DFT-SOFDM symbol reserved for SRS in asubframe. This can be indicated using a field in uplink grant to the UEscheduled for PUSCH transmission.

TABLE 1 One Bit Field Uplink Grant for PUSCH Transmission Field inUplink grant function comment 0 No SRS symbol in the Transmit PUSCHwithout subframe rate-matching around 1^(st) symbol 1 First symbol inthe Transmit PUSCH with subframe is reserved rate-matching around 1^(st)symbol for SRS

Alternatively, a two bit field can be used to explicitly indicatewhether there is an SRS symbol in the subframe, whether the UE's PUSCHhas to be rate-matched around the SRS symbol, and which configuration isused for transmitting the SRS in the first symbol.

TABLE 2 Two Bit Field Uplink Grant for PUSCH Transmission Field inUplink grant Function 00 No SRS symbol in the Transmit PUSCH withoutsubframe rate-matching around 1^(st) symbol 01 First symbol in theTransmit PUSCH with subframe is reserved rate-matching around 1^(st)symbol for SRS 10 First symbol in the Transmit PUSCH with subframe isreserved rate-matching around 1^(st) symbol, for SRS, transmit SRStransmit SRS in the first symbol using first configuration 11 Firstsymbol in the Transmit PUSCH with subframe is reserved rate-matchingaround 1^(st) symbol, for SRS, transmit SRS transmit SRS in the firstsymbol using second configuration

The UE may lose the channel if it does LBT, such as the case where CCAperformed by the UE is successful in the last symbol of the previoussubframe, the UE does not have to transmit in the first OFDM symbol ofthe subframe, and the UE can attempt to transmit PUSCH in the remainingsymbols of the subframe. Therefore, a UE that is configured to transmitPUSCH can always transmit SRS in the first symbol of the subframe, suchas an unsolicited SRS just prior to transmitting PUSCH. The ‘01’ or ‘1’value may then correspond to transmitting SRS using a thirdconfiguration, with SRS transmission in the first symbol.

For PUSCH and SRS transmission, a UE that is scheduled to transmit bothPUSCH and SRS transmission may transmit SRS in the first symbol of thesubframe, followed by PUSCH in the rest of the subframe. An explicitaperiodic SRS transmission indicator can be used to indicate to the UEwhether, and in which resources, the SRS is transmitted. In anotheralternative, a UE may be configured such that it performs LBT in 13^(th)DFT-SOFDM symbol of subframe n+3, transmit SRS in 14^(th) DFT-SOFDMsymbol, such as a last symbol, of subframe n+3, and then transmit PUSCHin subframe n+4 in first to 12^(th) DFT-SOFDM symbols, so it can againperform LBT in 13^(th) symbol of subframe n+4.

FIG. 7 is an example flowchart 700 illustrating a user equipmentprocedure for transmitting the SRS according to a possible embodiment.At 710, the flowchart 700 can begin. At 720, an uplink grant can bereceived. The uplink grant can include a field requesting the SRStransmission. The uplink grant can also include a field indicating a SRSresource in the DFT-SOFDM symbol for transmission of SRS. The uplinkgrant can additionally include a field that indicates there is no SRS inthe subframe. The uplink grant can further include a field thatindicates a configuration for transmitting the SRS. Alternately, or inaddition to receiving the uplink grant, a signal can received thatindicates avoiding PUSCH mapping in the first DFT-SOFDM symbol of asubframe. PUSCH mapping can be abstained in the first DFT-SOFDM symbolof the subframe in response to receiving the signal that indicatesavoiding PUSCH mapping in the first DFT-SOFDM symbol of the subframe.

At 730, listen before talk can be performed to determine when a subframeis available for uplink transmission. The listen before talk procedurecan be performed on an unlicensed carrier in response to receiving theuplink grant. At 740, a SRS can be transmitted in a first DFT-SOFDMsymbol of the subframe when listen before talk indicates that thesubframe is available. Transmission of SRS in the first DFT-SOFDM symbolcan be performed in response to the field in the uplink grant requestingthe SRS transmission. Transmission of the SRS in the first DFT-SOFDMsymbol can also be performed in the SRS resource indicated by the fieldin the uplink grant. Transmission of the SRS in the first DFT-SOFDMsymbol can additionally be performed even when the field that indicatesthere is no SRS in the subframe. Transmission of the SRS in the firstDFT-SOFDM symbol can further be performed based on the field indicatingthe configuration for transmitting the SRS.

At 750, a PUSCH can be transmitted in at least a portion of a remainingpart of the subframe. The portion of the remaining part of the subframecan exclude at least the last DFT-SOFDM symbol of the subframe. At 760,the flowchart 700 can end.

According to a possible embodiment, the eNB can include a HARQ ID, suchas an UL HARQ ID, in the grant sent to the UE. While transmitting PUSCHin response to the grant, the UE can send the HARQ ID, such as the ULHARQ ID, along with the PUSCH transmission. For the second optiondiscussed before, the UE can include both the HARQ ID and the HARQ-subIDalong with its PUSCH transmissions. The HARQ ID/HARQ subID can betransmitted by the UE using different approaches. For a first approach,a one-to-one mapping can be specified between UL HARQ ID and DMRS cyclicshift value. The UE can receive the UL HARQ ID in the UL grant and canuse the corresponding DMRS cyclic shift value determined from thepre-specified mapping for transmitting or retransmitting PUSCHassociated with that UL HARQ ID. For example, if the UL grant containsUL HARQ ID (x), the UE can transmit the corresponding PUSCH using DMRScyclic shift x.

For a second approach, the UE can multiplex bits indicating HARQ ID, andHARQ subID if needed, within its PUSCH transmission. The uplink HARQ ID,and HARQ subID if needed, can be multiplexed within PUSCH usingdifferent methods. One method for multiplexing the uplink HARQ ID, andHARQ subID if needed, can use Uplink Control Information (UCI)multiplexing type 1. In this case, the uplink HARQ ID, such as a HARQ IDhaving <3 bits, can be encoded using a block code to a particular codeand the number of resource elements for transmission of the uplink HARQID can be determined, based on the uplink data MCS. The encoded uplinkHARQ ID can mapped to a subset of resource elements from the set ofresource elements assigned for PUSCH transmission. This subset can bedetermined based on a predetermined rule, such as in a set of or portionof DFT-SOFDM symbols in the subframe, such as OFDM symbols 1, 2, or in aset of resources, such as lowest indexed modulation symbolscorresponding to the resource assignment. A similar approach can be usedfor HARQ subID, such as with 2 additional bits, with possibly jointencoding with the HARQ ID.

Another method for multiplexing the uplink HARQ ID, and HARQ subID ifneeded, can multiplex the UL HARQ ID with uplink data using variousadditional methods. One method for multiplexing the UL HARQ ID withuplink data can use rate-matching. In this case, the encoded uplink HARQID can be mapped to a subset of modulation symbols and the encoded datacan be mapped to the remaining subset of modulation symbols assigned forPUSCH transmission. This can be a useful mechanism if the eNB is awarethat the encoded uplink HARQ ID is always sent by the UE. A similarapproach can be used for a HARQ subID. Another method for multiplexingthe UL HARQ ID with uplink data can use puncturing. In this case, theencoded data can be mapped to the all of the modulation symbols assignedfor PUSCH transmission and the uplink HARQ ID can be mapped to a subsetof modulation symbols, overwriting any encoded data. This can be auseful mechanism if the eNB is not always sure if the encoded uplinkHARQ ID is always sent by the UE. Thus, in cases where the encodeduplink HARQ ID is not transmitted, the UE can use the subset ofmodulation symbols for PUSCH to improve the data performance. A similarapproach can be used for a HARQ subID.

In another method for multiplexing the uplink HARQ ID, and HARQ subID ifneeded, for UL-MIMO, the uplink HARQ ID information may be multiplexedwith data on both UL-SCH transport blocks and possibly on the samemodulation symbol resources. Other methods for multiplexing the uplinkHARQ ID, and HARQ subID if needed, can include other types of UCImultiplexing on PUSCH, such as methods used in LTE for multiplexing CQI(Channel Quality Indicator) or PMI (Precoder Matrix Indicator) or RI(Rank Indicator) or HARQ-ACK (Hybrid ARQ Acknowledgments), and othermethods.

The HARQ ID may be encoded in multiple ways. For one way of encoding aHARQ ID, a CRC may be attached and the CRC-encoded HARQ ID may be codedusing a block code such as Reed-Muller code or convolutional code. Thiscan allow an eNB to reliably detect the HARQ-ID. A similar approach canbe used for a HARQ subID. The HARQ ID can also be directly encoded usinga block code such as Reed-Muller code or convolutional code. Since thereis no CRC, there may be no reliable error detection, but this can enablea lower coding rate, which can result in improved performance. A similarapproach can be used for a HARQ subID. For 1 or 2 bit HARQ ID/sub ID,the HARQ ID/sub ID bits can be mapped to a Binary Phase Shift Keying(BPSK)/Quadrature Phase Shift Keying (QPSK) symbol, and the BPSK/QPSKsymbol can be used to modulate one of the demodulation reference signalsin the subframe.

The UE can indicate UL HARQ ID using a first method (for example, usingthe first approach described above) and UL HARQ subID using a secondmethod (for example, using the second approach described above).

FIG. 8 is an example block diagram of an apparatus 800, such as the UE110 or the UE 112, according to a possible embodiment. The apparatus 800can include a housing 810, a controller 820 within the housing 810,audio input and output circuitry 830 coupled to the controller 820, adisplay 840 coupled to the controller 820, a transceiver 850 coupled tothe controller 820, an antenna 855 coupled to the transceiver 850, auser interface 860 coupled to the controller 820, a memory 870 coupledto the controller 820, and a network interface 880 coupled to thecontroller 820. The apparatus 800 can perform the methods described inall the embodiments.

The display 840 can be a viewfinder, a liquid crystal display (LCD), alight emitting diode (LED) display, a plasma display, a projectiondisplay, a touch screen, or any other device that displays information.The transceiver 850 can include a transmitter and/or a receiver. Theaudio input and output circuitry 830 can include a microphone, aspeaker, a transducer, or any other audio input and output circuitry.The user interface 860 can include a keypad, a keyboard, buttons, atouch pad, a joystick, a touch screen display, another additionaldisplay, or any other device useful for providing an interface between auser and an electronic device. The network interface 880 can be auniversal serial bus port, an Ethernet port, an infraredtransmitter/receiver, a USB port, an IEEE 1398 port, a WLAN transceiver,or any other interface that can connect an apparatus to a network orcomputer and that can transmit and receive data communication signals.The memory 870 can include a random access memory, a read only memory,an optical memory, a flash memory, a removable memory, a hard drive, acache, or any other memory that can be coupled to a wirelesscommunication device.

The apparatus 800 or the controller 820 may implement any operatingsystem, such as Microsoft Windows®, UNIX®, or LINUX®, Android™, or anyother operating system. Apparatus operation software may be written inany programming language, such as C, C++, Java or Visual Basic, forexample. Apparatus software may also run on an application framework,such as, for example, a Java® framework, a .NET® framework, or any otherapplication framework. The software and/or the operating system may bestored in the memory 870 or elsewhere on the apparatus 800. Theapparatus 800 or the controller 820 may also use hardware to implementdisclosed operations. For example, the controller 820 may be anyprogrammable processor. Disclosed embodiments may also be implemented ona general-purpose or a special purpose computer, a programmedmicroprocessor or microprocessor, peripheral integrated circuitelements, an application-specific integrated circuit or other integratedcircuits, hardware/electronic logic circuits, such as a discrete elementcircuit, a programmable logic device, such as a programmable logicarray, field programmable gate-array, or the like. In general, thecontroller 820 may be any controller or processor device or devicescapable of operating an electronic device and implementing the disclosedembodiments.

In operation according to a possible embodiment, the transceiver 850 canreceive a configuration indicating a window length from a higher layer,where the higher layer is higher than a physical layer. The transceiver850 can also receive a grant in a subframe, where the grant can be fortransmitting a PUSCH on a serving cell operating on an unlicensedcarrier. The grant for transmitting the PUSCH can include a HARQ ID.

The controller 820 can determine a set of subframes for possibletransmission of the PUSCH based on the window length and the subframe inwhich the grant is received. The set of subframes can include a numberof subframes, where the number of subframes in the set of subframes canbe equal to the window length. The controller 820 can also perform LBTon the unlicensed carrier to determine an earliest unoccupied subframein the set of subframes.

The transceiver 850 can transmit the PUSCH in the earliest unoccupiedsubframe in response to receiving the grant. The transceiver 850 cantransmit the PUSCH in the earliest unoccupied subframe if the unoccupiedsubframe is unoccupied and if the unoccupied subframe is within thewindow length. The transceiver 850 can indicate the HARQ ID along withthe PUSCH transmission. According to a possible implementation, thecontroller 820 can determine a demodulation reference signal cyclicshift value based on the HARQ ID and the transceiver 850 can transmit ademodulation reference signal using the determined cyclic shift value,along with the PUSCH transmission. According to another possibleimplementation, the transceiver 850 can indicate the HARQ ID along withthe PUSCH transmission by multiplexing bits indicating the HARQ ID intoa portion of resources assigned for the PUSCH transmission.

The transceiver 850 can also receive a second grant in a secondsubframe, where the second grant can be for transmitting a second PUSCHon the serving cell operating on the unlicensed carrier. The controller820 can determine a second set of subframes for possible transmission ofthe second PUSCH based on the window length and the second subframe inwhich the second grant is received. The determined earliest unoccupiedsubframe can be a subframe in the second set of subframes. Thecontroller 820 can then prioritize one of multiple PUSCH transmissionsbased on the order in which each corresponding PUSCH grant is received.The transceiver 850 can then transmit the prioritized PUSCH transmissionin the earliest unoccupied subframe.

The controller 820 can perform LBT a first subframe in the set ofsubframes, can determine the first subframe in the set of subframes isoccupied, and can perform LBT on subsequent subframes in the set ofsubframes to determine an earliest unoccupied subframe in the set ofsubframes. The controller 820 can determine none of the subframes in theset of subframes are free for PUSCH transmission based on performingLBT, and can skip transmitting PUSCH for the grant if none of thesubframes in the set of subframes are free for PUSCH transmission.

In operation according to another possible embodiment, the transceiver850 can receive, in a subframe, a grant for transmitting PUSCH on aserving cell operating on an unlicensed spectrum. The grant fortransmitting PUSCH can include a HARQ ID. The controller 820 candetermine a set of subframes for possible transmission of the PUSCH andperform LBT on the unlicensed carrier to determine an earliestunoccupied subframe in the set of subframes.

The transceiver 850 can transmit a PUSCH in multiple subframes withinthe set of subframes on the unlicensed carrier, starting with theearliest unoccupied subframe, in response to receiving the grant. Thetransceiver 850 can include the HARQ ID in each PUSCH transmission inthe multiple subframes. The transceiver 850 can also include a HARQsubID along with each PUSCH transmission in the multiple subframes. TheHARQ subID can be for a particular PUSCH transmission in the multiplesubframes. The HARQ subID can be set to 0 for the first PUSCHtransmission, can be set to 1 for the second PUSCH transmission, and canbe incremented for each subsequent PUSCH transmission.

The controller 820 can determine a new HARQ ID for each PUSCHtransmission made in response to the grant. The new HARQ ID can bedetermined based on the received HARQ ID and an order of the PUSCHtransmission within the PUSCH transmission in the multiple subframes.The transceiver 850 can transmit each new HARQ ID along with each PUSCHtransmission.

The new HARQ ID can also be determined based on the received HARQ ID anda subframe index of the subframe where each PUSCH transmission is made.The transceiver 850 can then receive a second grant requesting aretransmission. The second grant can include the new HARQ ID that waspreviously transmitted. The transceiver 850 can then transmit PUSCH inresponse to the second grant to retransmit the data that is associatedwith the same new HARQ ID.

In operation according to another possible embodiment, the transceiver850 can receive an uplink grant. The uplink grant can include a fieldrequesting the SRS transmission. The uplink grant can also include afield indicating a SRS resource in the DFT-SOFDM symbol for transmissionof SRS. The uplink grant can additionally include a field that indicatesthere is no SRS in the subframe. The uplink grant can further include afield that indicates a configuration for transmitting the SRS.

The controller 820 can perform LBT to determine when a subframe isavailable for uplink transmission. For example, the controller 820 canperform the LBT in response to the transceiver receiving the uplinkgrant. The controller 820 can perform LBT on an unlicensed carrier todetermine when a subframe is available for uplink transmission.

The transceiver 850 can transmit a SRS in a first DFT-SOFDM symbol ofthe subframe when LBT indicates that the subframe is available. Thetransmission of the SRS in the first DFT-SOFDM symbol can be performedin response to the field in the uplink grant requesting the SRStransmission. The transmission of the SRS in the first DFT-SOFDM symbolcan also be performed even when the field that indicates there is no SRSin the subframe. The transmission of the SRS in the first DFT-SOFDMsymbol can additionally be performed in the SRS resource indicated bythe field in the uplink grant. The transmission of the SRS in the firstDFT-SOFDM symbol can further be performed based on the field indicatingthe configuration for transmitting the SRS. The transceiver 850 cantransmit PUSCH in at least a portion of a remaining part of thesubframe. The portion of the remaining part of the subframe can excludeat least the last DFT-SOFDM symbol of the subframe.

The transceiver 850 can also receive a signal that indicates avoidingPUSCH mapping in the first DFT-SOFDM symbol of a subframe. Thecontroller 820 can then abstain from PUSCH mapping in the firstDFT-SOFDM symbol of the subframe in response to receiving the signalthat indicates avoiding PUSCH mapping in the first DFT-SOFDM symbol ofthe subframe.

FIG. 9 is an example block diagram of a base station 900, such as theeNB 120, according to a possible embodiment. The base station 900 mayinclude a controller 910, a memory 920, a database interface 930, atransceiver 940, Input/Output (I/O) device interface 950, a networkinterface 960, and a bus 970. The base station 900 can implement anyoperating system, such as Microsoft Windows®, UNIX, or LINUX, forexample. Base station operation software may be written in anyprogramming language, such as C, C++, Java or Visual Basic, for example.The base station software can run on an application framework, such as,for example, a Java® server, a .NET® framework, or any other applicationframework.

The transceiver 940 can create a data connection with the UE 110. Thecontroller 910 can be any programmable processor. Disclosed embodimentscan also be implemented on a general-purpose or a special purposecomputer, a programmed microprocessor or microprocessor, peripheralintegrated circuit elements, an application-specific integrated circuitor other integrated circuits, hardware/electronic logic circuits, suchas a discrete element circuit, a programmable logic device, such as aprogrammable logic array, field programmable gate-array, or the like. Ingeneral, the controller 910 can be any controller or processor device ordevices capable of operating a base station and implementing thedisclosed embodiments.

The memory 920 can include volatile and nonvolatile data storage,including one or more electrical, magnetic, or optical memories, such asa Random Access Memory (RAM), cache, hard drive, or other memory device.The memory 920 can have a cache to speed access to specific data. Thememory 920 can also be connected to a Compact Disc-Read Only Memory(CD-ROM), Digital Video Disc-Read Only memory (DVD-ROM), DVD read writeinput, tape drive, thumb drive, or other removable memory device thatallows media content to be directly uploaded into a system. Data can bestored in the memory 920 or in a separate database. For example, thedatabase interface 930 can be used by the controller 910 to access thedatabase. The database can contain any formatting data to connect theterminal 110 to the network 130.

The I/O device interface 950 can be connected to one or more input andoutput devices that may include a keyboard, a mouse, a touch screen, amonitor, a microphone, a voice-recognition device, a speaker, a printer,a disk drive, or any other device or combination of devices that acceptinput and/or provide output. The I/O device interface 950 can receive adata task or connection criteria from a network administrator. Thenetwork connection interface 960 can be connected to a communicationdevice, modem, network interface card, a transceiver, or any otherdevice capable of transmitting and receiving signals to and from thenetwork 130. The components of the base station 900 can be connected viathe bus 970, may be linked wirelessly, or may be otherwise connected.

Although not required, embodiments can be implemented usingcomputer-executable instructions, such as program modules, beingexecuted by an electronic device, such as a general purpose computer.Generally, program modules can include routine programs, objects,components, data structures, and other program modules that performparticular tasks or implement particular abstract data types. Theprogram modules may be software-based and/or may be hardware-based. Forexample, the program modules may be stored on computer readable storagemedia, such as hardware discs, flash drives, optical drives, solid statedrives, CD-ROM media, thumb drives, and other computer readable storagemedia that provide non-transitory storage aside from a transitorypropagating signal. Moreover, embodiments may be practiced in networkcomputing environments with many types of computer systemconfigurations, including personal computers, hand-held devices,multi-processor systems, microprocessor-based or programmable consumerelectronics, network personal computers, minicomputers, mainframecomputers, and other computing environments.

Embodiments can provide for a method including UE being configured byhigher layers with a window length (W) parameter, receiving a grant fortransmitting PUSCH on a serving cell operating in unlicensed spectrum,determining a set of subframes for possible transmission of PUSCH basedon W and the subframe in which the grant is received, performing listenbefore talk on the unlicensed carrier to determine the earliestunoccupied subframe in the set of subframes, and transmitting PUSCH inthat earliest subframe in response to the received grant. The method caninclude receiving a HARQ ID (x) in the grant and including the receivedHARQ ID (x) along with the PUSCH transmission. If multiple PUSCHtransmissions due to multiple received grants are possible in the samesubframe, the method can include prioritizing one of the multiple PUSCHtransmissions based on the order in which the grants corresponding tothe transmissions are received, and transmitting the prioritized PUSCHtransmission in the earliest subframe.

Embodiments can provide for a method including UE receiving a grant fortransmitting PUSCH on a serving cell operating in unlicensed spectrum,determining a set of subframes for possible transmission of PUSCH,performing listen before talk on the unlicensed carrier to determine theearliest unoccupied subframe in the set of subframes, and makingmultiple PUSCH transmissions in multiple subframes within the set ofsubframes, starting with the earliest unoccupied subframe, in responseto the received grant. The method can include determining the set ofsubframes for possible transmission of PUSCH using the subframe index ofthe subframe in which the grant is received and a window lengthparameter including a window length (W) that is either received in thegrant or configured via higher layers. The method can include receivinga HARQ ID (x) in the grant and including the received HARQ ID (x) ineach of the multiple PUSCH transmissions, in addition to the HARQ ID(x), including a HARQ subID (y) along with each of the multiple PUSCHtransmissions, where the HARQ subID can be set to 0 (y=0) for the firstPUSCH transmission, can be set to 1 (y=1) for the second PUSCHtransmission, etc. The method can include receiving a second grantrequesting a retransmission, wherein the second grant can include a HARQID and HARQ subID that was previously transmitted by the UE, andtransmitting PUSCH in response to the second grant to retransmit datathat is associated with the same HARQ ID and HARQ subID. The method caninclude receiving a HARQ ID (x) in the grant, determining a new HARQ ID(x′) for each PUSCH transmission made in response to the grant, andtransmitting the new HARQ ID (x′) along with each PUSCH transmission,where the new HARQ ID (x′) can be determined based on the received HARQID (x) and the order of the PUSCH transmission within the multiple PUSCHtransmissions. The method can include receiving a second grantrequesting a retransmission, where the second grant can include a HARQID (x′) that was previously transmitted by the UE, and transmittingPUSCH in response to the second grant to retransmit the data that isassociated with the same HARQ ID (x′). The method can include receivinga HARQ ID (x) in the grant, determining a new HARQ ID (x″) for eachPUSCH transmission made in response to the grant, where the new HARQ ID(x″) can be determined based on the received HARQ ID (x) and thesubframe index of the subframe where each PUSCH transmission is made,receiving a second grant requesting a retransmission, where the secondgrant can include a HARQ ID (x″) that was previously transmitted by theUE, and transmitting PUSCH in response to the second grant to retransmitthe data that is associated with the same HARQ ID (x″). The method caninclude receiving multiple New Data Indicators (NDI's) within the grant,where each NDI value can be associated with each subframe within thedetermined set of subframes for possible transmission of PUSCH, andtransmitting either new data or retransmission in that subframeaccording to the NDI value.

Embodiments can provide for a UE determining a minimum time forperforming clear channel assessment before determining that a carrier isunoccupied, a maximum channel occupancy time for contiguous transmissionon the carrier, and/or a starting position of a symbol within a subframefor initiating clear channel assessment; for performing LBT, based onsignaling received from eNB.

Embodiments can also provide for a method including a UE performing LBT,transmitting SRS in the first OFDM symbol of an uplink subframe if LBTpasses, and transmitting PUSCH in at least a portion of the remainingpart of the subframe.

The methods of this disclosure can be implemented on a programmedprocessor. However, the controllers, flowcharts, and modules may also beimplemented on a general purpose or special purpose computer, aprogrammed microprocessor or microcontroller and peripheral integratedcircuit elements, an integrated circuit, a hardware electronic or logiccircuit such as a discrete element circuit, a programmable logic device,or the like. In general, any device on which resides a finite statemachine capable of implementing the flowcharts shown in the figures maybe used to implement the processor functions of this disclosure.

While this disclosure has been described with specific embodimentsthereof, it is evident that many alternatives, modifications, andvariations will be apparent to those skilled in the art. For example,various components of the embodiments may be interchanged, added, orsubstituted in the other embodiments. Also, all of the elements of eachfigure are not necessary for operation of the disclosed embodiments. Forexample, one of ordinary skill in the art of the disclosed embodimentswould be enabled to make and use the teachings of the disclosure bysimply employing the elements of the independent claims. Accordingly,embodiments of the disclosure as set forth herein are intended to beillustrative, not limiting. Various changes may be made withoutdeparting from the spirit and scope of the disclosure.

In this document, relational terms such as “first,” “second,” and thelike may be used solely to distinguish one entity or action from anotherentity or action without necessarily requiring or implying any actualsuch relationship or order between such entities or actions. The phrase“at least one of” followed by a list is defined to mean one, some, orall, but not necessarily all of, the elements in the list. The terms“comprises,” “comprising,” or any other variation thereof, are intendedto cover a non-exclusive inclusion, such that a process, method,article, or apparatus that comprises a list of elements does not includeonly those elements but may include other elements not expressly listedor inherent to such process, method, article, or apparatus. An elementproceeded by “a,” “an,” or the like does not, without more constraints,preclude the existence of additional identical elements in the process,method, article, or apparatus that comprises the element. Also, the term“another” is defined as at least a second or more. The terms“including,” “having,” and the like, as used herein, are defined as“comprising.” Furthermore, the background section is written as theinventor's own understanding of the context of some embodiments at thetime of filing and includes the inventor's own recognition of anyproblems with existing technologies and/or problems experienced in theinventor's own work.

1. A method in a user equipment, the method comprising: receiving aconfiguration indicating a window length from a higher layer, where thehigher layer is higher than a physical layer; receiving a grant in asubframe, the grant for transmitting a physical uplink shared channel ona serving cell operating on an unlicensed carrier; determining a set ofsubframes for possible transmission of the physical uplink sharedchannel based on the window length and the subframe in which the grantis received; performing listen before talk on the unlicensed carrier todetermine an earliest unoccupied subframe in the set of subframes; andtransmitting the physical uplink shared channel in the earliestunoccupied subframe in response to receiving the grant.
 2. The methodaccording to claim 1, wherein transmitting comprises transmitting thephysical uplink shared channel in the earliest unoccupied subframe whenthe subframe is unoccupied and when the subframe is within the windowlength.
 3. The method according to claim 1, wherein the grant fortransmitting the physical uplink shared channel includes a hybridautomatic retransmission request identifier, and wherein the methodfurther comprises indicating the hybrid automatic retransmission requestidentifier along with the physical uplink shared channel transmission.4. The method according to claim 3, wherein indicating the hybridautomatic retransmission request identifier along with the physicaluplink shared channel transmission comprises: determining a demodulationreference signal cyclic shift value based on the hybrid automaticretransmission request identifier; and transmitting a demodulationreference signal using the determined cyclic shift value, along with thephysical uplink shared channel transmission.
 5. The method according toclaim 3, wherein indicating the hybrid automatic retransmission requestidentifier along with the physical uplink shared channel transmissioncomprises multiplexing bits indicating the hybrid automaticretransmission request identifier into a portion of resources assignedfor the physical uplink shared channel transmission.
 6. The methodaccording to claim 1, further comprising: receiving a second grant in asecond subframe, where the second grant is for transmitting a secondphysical uplink shared channel on the serving cell operating on theunlicensed carrier; determining a second set of subframes for possibletransmission of the second physical uplink shared channel based on thewindow length and the second subframe in which the second grant isreceived, where the determined earliest unoccupied subframe is asubframe in the second set of subframes; and prioritizing one ofmultiple physical uplink shared channel transmissions based on the orderin which each corresponding physical uplink shared channel grant isreceived when the earliest unoccupied subframe corresponding to thefirst grant and second grant is the same, wherein transmitting comprisestransmitting the prioritized physical uplink shared channel transmissionin the earliest unoccupied subframe.
 7. The method according to claim 1,wherein performing listen before talk comprises: performing listenbefore talk on a first resource associated with a first subframe in theset of subframes; determining that the first subframe in the set ofsubframes is occupied; and performing listen before talk on resourcesassociated with subsequent subframes in the set of subframes todetermine an earliest unoccupied subframe in the set of subframes. 8.The method according to claim 7, further comprising: determining none ofthe subframes in the set of subframes are unoccupied for physical uplinkshared channel transmission based on performing listen before talk; andskipping transmitting physical uplink shared channel for the grant whennone of the subframes in the set of subframes are unoccupied forphysical uplink shared channel transmission.
 9. The method according toclaim 1, wherein the set of subframes includes a number of subframes,where the number of subframes in the set of subframes is equal to thewindow length.
 10. The method according to claim 1, wherein theconfiguration indicating a window length comprises at least one of anexplicit window length indication and a pointer to a window length fromwhich window length is determined using a look-up table.
 11. Anapparatus comprising: a transceiver configured to receive aconfiguration indicating a window length from a higher layer, where thehigher layer is higher than a physical layer, and configured to receivea grant in a subframe, the grant for transmitting a physical uplinkshared channel on a serving cell operating on an unlicensed carrier; anda controller coupled to the transceiver, the controller configured todetermine a set of subframes for possible transmission of the physicaluplink shared channel based on the window length and the subframe inwhich the grant is received, and configured to perform listen beforetalk on the unlicensed carrier to determine an earliest unoccupiedsubframe in the set of subframes, wherein the transceiver is configuredto transmit the physical uplink shared channel in the earliestunoccupied subframe in response to receiving the grant.
 12. Theapparatus according to claim 11, wherein the transceiver is configuredto transmit the physical uplink shared channel in the earliestunoccupied subframe when the subframe is unoccupied and when thesubframe is within the window length.
 13. The apparatus according toclaim 11, wherein the grant for transmitting the physical uplink sharedchannel includes a hybrid automatic retransmission request identifier,and wherein the transceiver is configured to indicate the hybridautomatic retransmission request identifier along with the physicaluplink shared channel transmission.
 14. The apparatus according to claim13, wherein the controller is configured to determine a demodulationreference signal cyclic shift value based on the hybrid automaticretransmission request identifier, and wherein transceiver is configuredto transmit a demodulation reference signal using the determined cyclicshift value, along with the physical uplink shared channel transmission.15. The apparatus according to claim 13, wherein the transceiver isconfigured to indicate the hybrid automatic retransmission requestidentifier along with the physical uplink shared channel transmission bymultiplexing bits indicating the hybrid automatic retransmission requestidentifier into a portion of resources assigned for the physical uplinkshared channel transmission.
 16. The apparatus according to claim 11,wherein the transceiver is configured to receive a second grant in asecond subframe, where the second grant is for transmitting a secondphysical uplink shared channel on the serving cell operating on theunlicensed carrier, wherein the controller is configured to determine asecond set of subframes for possible transmission of the second physicaluplink shared channel based on the window length and the second subframein which the second grant is received, where the determined earliestunoccupied subframe is a subframe in the second set of subframes, and isconfigured to prioritize one of multiple physical uplink shared channeltransmissions based on the order in which each corresponding physicaluplink shared channel grant is received when the earliest unoccupiedsubframe corresponding to the first grant and second grant is the same,and wherein the transceiver is configured to transmit by transmittingthe prioritized physical uplink shared channel transmission in theearliest unoccupied subframe.
 17. The apparatus according to claim 11,wherein the controller is configured to perform listen before talk byperforming listen before talk on a first resource associated with afirst subframe in the set of subframes, determining the first subframein the set of subframes is occupied, and performing listen before talkon resources associated with subsequent subframes in the set ofsubframes to determine an earliest unoccupied subframe in the set ofsubframes.
 18. The apparatus according to claim 17, wherein thecontroller is configured to determine none of the subframes in the setof subframes are unoccupied for physical uplink shared channeltransmission based on performing listen before talk, and configured toskip transmitting physical uplink shared channel for the grant when noneof the subframes in the set of subframes are unoccupied for physicaluplink shared channel transmission.
 19. The apparatus according to claim11, wherein the set of subframes includes a number of subframes, wherethe number of subframes in the set of subframes is equal to the windowlength.
 20. A method in a user equipment, the method comprising:receiving a configuration indicating a window length from a higher layerin a long term evolution system, where the higher layer is higher than aphysical layer; receiving a grant in a subframe, the grant fortransmitting a physical uplink shared channel on a serving celloperating on an unlicensed carrier in the long term evolution system;determining a set of subframes for possible transmission of the physicaluplink shared channel based on the window length and the subframe inwhich the grant is received, where the set of subframes includes anumber of subframes, where the number of subframes in the set ofsubframes is equal to the window length; performing listen before talkon the unlicensed carrier to determine an earliest unoccupied subframein the set of subframes; and transmitting the physical uplink sharedchannel in the earliest unoccupied subframe when the unoccupied subframeis unoccupied and when the unoccupied subframe is within the windowlength.
 21. The method according to claim 20, wherein the grant fortransmitting the physical uplink shared channel includes a hybridautomatic retransmission request identifier, and wherein the methodfurther comprises indicating the hybrid automatic retransmission requestidentifier along with the physical uplink shared channel transmission.